cmd/tailscale/cli: fix "subcommand required" errors when typod

Fixes tailscale#11672

Signed-off-by: Paul Scott <paul@tailscale.com>

cmd/tailscale/cli/cli.go

@@ -99,15 +99,32 @@ func Run(args []string) (err error) {
 		if errors.Is(err, flag.ErrHelp) {
 			return nil
 		}
+		if noexec := (ffcli.NoExecError{}); errors.As(err, &noexec) {
+			// When the user enters an unknown subcommand, ffcli tries to run
+			// the closest valid parent subcommand with everything else as args,
+			// returning NoExecError if it doesn't have an Exec function.
+			cmd := noexec.Command
+			args := cmd.FlagSet.Args()
+			if len(cmd.Subcommands) > 0 {
+				if len(args) > 0 {
+					return fmt.Errorf("%s: unknown subcommand: %s", fullCmd(rootCmd, cmd), args[0])
+				}
+				subs := make([]string, 0, len(cmd.Subcommands))
+				for _, sub := range cmd.Subcommands {
+					subs = append(subs, sub.Name)
+				}
+				return fmt.Errorf("%s: missing subcommand: %s", fullCmd(rootCmd, cmd), strings.Join(subs, ", "))
+			}
+		}
 		return err
 	}
 
 	if envknob.Bool("TS_DUMP_HELP") {
 		walkCommands(rootCmd, func(w cmdWalk) bool {
 			fmt.Println("===")
-			c := w.cmd
 			// UsageFuncs are typically called during Command.Run which ensures
 			// FlagSet is not nil.
+			c := w.Command
 			if c.FlagSet == nil {
 				c.FlagSet = flag.NewFlagSet(c.Name, flag.ContinueOnError)
 			}
@@ -182,7 +199,12 @@ change in the future.
 			driveCmd,
 		},
 		FlagSet: rootfs,
-		Exec:    func(context.Context, []string) error { return flag.ErrHelp },
+		Exec: func(ctx context.Context, args []string) error {
+			if len(args) > 0 {
+				return fmt.Errorf("tailscale: unknown subcommand: %s", args[0])
+			}
+			return flag.ErrHelp
+		},
 	}
 	if envknob.UseWIPCode() {
 		rootCmd.Subcommands = append(rootCmd.Subcommands,
@@ -195,8 +217,8 @@ change in the future.
 	}
 
 	walkCommands(rootCmd, func(w cmdWalk) bool {
-		if w.cmd.UsageFunc == nil {
-			w.cmd.UsageFunc = usageFunc
+		if w.UsageFunc == nil {
+			w.UsageFunc = usageFunc
 		}
 		return true
 	})
@@ -220,10 +242,24 @@ var rootArgs struct {
 }
 
 type cmdWalk struct {
-	cmd     *ffcli.Command
+	*ffcli.Command
 	parents []*ffcli.Command
 }
 
+func (w cmdWalk) Path() string {
+	if len(w.parents) == 0 {
+		return w.Name
+	}
+
+	var sb strings.Builder
+	for _, p := range w.parents {
+		sb.WriteString(p.Name)
+		sb.WriteString(" ")
+	}
+	sb.WriteString(w.Name)
+	return sb.String()
+}
+
 // walkCommands calls f for root and all of its nested subcommands until f
 // returns false or all have been visited.
 func walkCommands(root *ffcli.Command, f func(w cmdWalk) (more bool)) {
@@ -243,6 +279,21 @@ func walkCommands(root *ffcli.Command, f func(w cmdWalk) (more bool)) {
 	walk(root, nil, f)
 }
 
+// fullCmd returns the full "tailscale ... cmd" invocation for a subcommand.
+func fullCmd(root, cmd *ffcli.Command) (full string) {
+	walkCommands(root, func(w cmdWalk) bool {
+		if w.Command == cmd {
+			full = w.Path()
+			return false
+		}
+		return true
+	})
+	if full == "" {
+		return cmd.Name
+	}
+	return full
+}
+
 // usageFuncNoDefaultValues is like usageFunc but doesn't print default values.
 func usageFuncNoDefaultValues(c *ffcli.Command) string {
 	return usageFuncOpt(c, false)

cmd/tailscale/cli/cli_test.go

@@ -40,7 +40,7 @@ func TestShortUsage(t *testing.T) {
 	}
 
 	walkCommands(newRootCmd(), func(w cmdWalk) bool {
-		c, parents := w.cmd, w.parents
+		c, parents := w.Command, w.parents
 
 		// Words that we expect to be in the usage.
 		words := make([]string, len(parents)+1)

cmd/tailscale/cli/configure.go

@@ -4,7 +4,6 @@
 package cli
 
 import (
-	"context"
 	"flag"
 	"runtime"
 	"strings"
@@ -26,9 +25,6 @@ services on the host to use Tailscale in more ways.
 		return fs
 	})(),
 	Subcommands: configureSubcommands(),
-	Exec: func(ctx context.Context, args []string) error {
-		return flag.ErrHelp
-	},
 }
 
 func configureSubcommands() (out []*ffcli.Command) {

cmd/tailscale/cli/debug.go

@@ -346,7 +346,7 @@ func outName(dst string) string {
 
 func runDebug(ctx context.Context, args []string) error {
 	if len(args) > 0 {
-		return errors.New("unknown arguments")
+		return fmt.Errorf("tailscale debug: unknown subcommand: %s", args[0])
 	}
 	var usedFlag bool
 	if out := debugArgs.cpuFile; out != "" {
@@ -401,7 +401,7 @@ func runDebug(ctx context.Context, args []string) error {
 		// to subcommands.
 		return nil
 	}
-	return errors.New("see 'tailscale debug --help")
+	return errors.New("tailscale debug: subcommand or flag required")
 }
 
 func runLocalCreds(ctx context.Context, args []string) error {

cmd/tailscale/cli/drive.go

@@ -5,7 +5,6 @@ package cli
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"strings"
 
@@ -57,9 +56,6 @@ var driveCmd = &ffcli.Command{
 			Exec:       runDriveList,
 		},
 	},
-	Exec: func(context.Context, []string) error {
-		return errors.New("drive subcommand required; run 'tailscale drive -h' for details")
-	},
 }
 
 // runDriveShare is the entry point for the "tailscale drive share" command.

cmd/tailscale/cli/exitnode.go

@@ -25,10 +25,6 @@ func exitNodeCmd() *ffcli.Command {
 		Name:       "exit-node",
 		ShortUsage: "tailscale exit-node [flags]",
 		ShortHelp:  "Show machines on your tailnet configured as exit nodes",
-		LongHelp:   "Show machines on your tailnet configured as exit nodes",
-		Exec: func(context.Context, []string) error {
-			return errors.New("exit-node subcommand required; run 'tailscale exit-node -h' for details")
-		},
 		Subcommands: append([]*ffcli.Command{
 			{
 				Name:       "list",

cmd/tailscale/cli/file.go

@@ -44,12 +44,6 @@ var fileCmd = &ffcli.Command{
 		fileCpCmd,
 		fileGetCmd,
 	},
-	Exec: func(context.Context, []string) error {
-		// TODO(bradfitz): is there a better ffcli way to
-		// annotate subcommand-required commands that don't
-		// have an exec body of their own?
-		return errors.New("file subcommand required; run 'tailscale file -h' for details")
-	},
 }
 
 type countingReader struct {

cmd/tailscale/cli/network-lock.go

@@ -26,7 +26,7 @@ import (
 
 var netlockCmd = &ffcli.Command{
 	Name:       "lock",
-	ShortUsage: "tailscale lock <sub-command> <arguments>",
+	ShortUsage: "tailscale lock <subcommand> [arguments...]",
 	ShortHelp:  "Manage tailnet lock",
 	LongHelp:   "Manage tailnet lock",
 	Subcommands: []*ffcli.Command{
@@ -49,6 +49,9 @@ func runNetworkLockNoSubcommand(ctx context.Context, args []string) error {
 	if len(args) >= 2 && args[0] == "tskey-wrap" {
 		return runTskeyWrapCmd(ctx, args[1:])
 	}
+	if len(args) > 0 {
+		return fmt.Errorf("tailscale lock: unknown subcommand: %s", args[0])
+	}
 
 	return runNetworkLockStatus(ctx, args)
 }
@@ -195,6 +198,10 @@ var nlStatusCmd = &ffcli.Command{
 }
 
 func runNetworkLockStatus(ctx context.Context, args []string) error {
+	if len(args) > 0 {
+		return fmt.Errorf("tailscale lock status: unexpected argument")
+	}
+
 	st, err := localClient.NetworkLockStatus(ctx)
 	if err != nil {
 		return fixTailscaledConnectError(err)